Determination, Removal And Catalytic Oxidative Degradation Of Pesticide Residues

Pesticide residues have brought serious threat to the environment and human health. Thus, it is particularly significant to strengthen the detection of pesticides and investigate the removal, even complete degradation of pesticide residues in food and water. Financially supported by Natural Science Foundation of China and enterprise-funded project, this paper carries out a systematic study on determination and removal of three organophosphorous pesticides (dichlorvos, dimethoate, chlorpyrifos) in vegetables and on rapid degradation of those pesticides in wastewater.Based on correlative references, a simple method was developed to detect pesticides in vegetables using gas chromatography and to study the efficiency of removing pesticides residue in vegetables by self-prepared detergents. Matrix Solid-Phase Disperse was employed to prepare samples, using Florisil as dispersant and acetone/n-hexane as eluting solvent in this paper. Under optimal condition, the determination limits were 0.003 mg/kg~0.006 mg/kg, with quantification limits from 0.02 mg/kg to 0.03 mg/kg and relative standard deviation less than 8%. Special detergents were prepared using salt as the main material and some surfactants as additives. Experiments revealed that the as-prepared salt detergents have better washing and bactericidal effectiveness. The removal rates of pesticides in vegetables by the salt detergents ranged from 70% to 94%, which were higher than that of the commercial detergents obtained from the market. In addition, the levels of pesticides residue were far below the maximum residue level after vegetables were treated with the as-prepared salt detergents.Catalytic oxidation is one of the effective methods used in wastewater treatment. In this paper, nano-structured MnO2 was employed as catalyst to catalyze H2O2 oxidative degradation of pesticides in wastewater. Since the structure and morphology of catalysts greatly influence their catalytic performance, various factors, including reaction temperature, reaction time and reactant molar ratio which affect their structure and morphology, were investigated during the formation process of nano-structured MnO2. Withα-MnO2 nanorods as catalyst, the effects of various parameters, such as the amount of catalyst and H2O2 and the initial concentration of pesticides, on the catalytic degradation of three pesticides were studied. Experiments showed that the decoloration rates of 4μg/mL dichlorvos, dimethoate and chlorpyrifos reached 100%, 98.5% and 97.9% respectively when the reaction was carried out under the optimal catalytic condition. However, the degradation rates of pesticides decreased with the increase of the initial concentration of pesticides.